Characterization of solid catalysts

Abstract

Examples described herein provide a method for characterizing a catalyst in a chemisorption unit. The method includes treating a catalyst sample with gas blend comprising ammonia in an inert gas and performing a first temperature programmed desorption (TPD) to desorb the ammonia from the catalyst sample. A temperature programmed reduction (TPR) of the catalyst sample is performed with hydrogen. The catalyst sample is treated after the TPR with a gas blend comprising ammonia in an inert gas. A second temperature programmed desorption is performed to desorb the ammonia from the catalyst sample.

What is claimed is: 
     
         1 . A method for characterizing a catalyst in a chemisorption unit, comprising:
 treating a catalyst sample with a gas blend comprising ammonia in an inert gas;   performing a first temperature programmed desorption (TPD) to desorb the ammonia from the catalyst sample;   performing a temperature programmed reduction (TPR) of the catalyst sample with hydrogen;   treating the catalyst sample after the TPR with a gas blend comprising ammonia in an inert gas; and   performing a second temperature programmed desorption (TPD) to desorb the ammonia from the catalyst sample.   
     
     
         2 . The method of  claim 1 , comprising:
 loading the catalyst sample in the chemisorption unit; and   drying the catalyst sample by flowing the inert gas over the catalyst sample while ramping a temperature of the catalyst sample from about 50° C. to about 500° C. at about 10° C./min.   
     
     
         3 . The method of  claim 1 , wherein treating the catalyst sample with a gas blend comprises flowing a blend of 10% ammonia in helium at a flow rate of about 30 cc/min for about 35 minutes at about 50° C. 
     
     
         4 . The method of  claim 1 , wherein performing the first temperature programmed desorption comprises:
 flowing a carrier gas over the catalyst sample, wherein the carrier gas comprises helium;   ramping a temperature of the catalyst sample from about 50° C. to about 550° C. at about 10° C./min; and   collecting data from a thermal conductivity detector to measure ammonia desorbed at a temperature during the ramping.   
     
     
         5 . The method of  claim 1 , comprising measuring an amount of the ammonia desorbed from the catalyst sample during the first TPD versus time by plotting a response from a thermal conductivity detector versus temperature. 
     
     
         6 . The method of  claim 5 , comprising measuring a total acidity of the catalyst sample by integrating an area of a measured response from the thermal conductivity detector. 
     
     
         7 . The method of  claim 5 , comprising determining a relative acid strength of the catalyst sample by comparing peak locations of the ammonia released from other catalyst samples. 
     
     
         8 . The method of  claim 5 , comprising cooling the catalyst sample under a flow of the inert gas. 
     
     
         9 . The method of  claim 1 , comprising measuring an amount of hydrogen adsorbed by the catalyst sample during the TPR by measuring an amount of hydrogen removed from a carrier gas. 
     
     
         10 . The method of  claim 1 , wherein performing the TPR of the catalyst sample with hydrogen comprises:
 flowing a carrier gas over the catalyst sample, wherein the carrier gas comprises a gas blend of 5% hydrogen in argon;   ramping the temperature of the catalyst sample from about 50° C. to about 800° C. at about 10° C./min; and   collecting data from a thermal conductivity detector to measure an amount of hydrogen removed from the carrier gas at a temperature during the ramping.   
     
     
         11 . The method of  claim 10 , comprising determining an activity of the catalyst sample by integrating peaks of the hydrogen adsorbed during the TPR. 
     
     
         12 . The method of  claim 10 , comprising determining a number of active sites of the catalyst sample by determining a number of peaks in a plot of the TPR. 
     
     
         13 . The method of  claim 10 , comprising dispersing at least a portion of metal sites by performing the TPR. 
     
     
         14 . The method of  claim 1 , wherein treating the catalyst sample after the TPR comprises flowing a gas blend comprising 10% ammonia in helium over the catalyst sample at a flow rate of about 30 cc/min for about 35 minutes at about 50° C. 
     
     
         15 . The method of  claim 14 , wherein performing the second temperature programmed desorption comprises:
 flowing a carrier gas over the catalyst sample, wherein the carrier gas comprises helium;   ramping the temperature of the catalyst sample from about 50° C. to about 550° C. at about 10° C./min; and   collecting data from a thermal conductivity detector to measure ammonia desorbed at a temperature during the ramping.   
     
     
         16 . The method of  claim 14 , comprising measuring an amount of the ammonia desorbed from the catalyst sample during the second TPD versus time by plotting a response from a thermal conductivity detector versus temperature. 
     
     
         17 . The method of  claim 16 , comprising measuring a total acidity of the catalyst sample by integrating an area of a measured response from the thermal conductivity detector. 
     
     
         18 . The method of  claim 16 , comprising determining a relative acid strength of the catalyst sample by comparing peak locations of the ammonia released from other catalyst samples. 
     
     
         19 . The method of  claim 1 , comprising determining a change in acid strength of the catalyst sample by comparing results from the second temperature programmed desorption to results of the first temperature programmed desorption.